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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] | The components of accumulated other comprehensive income (loss) included in stockholders’ equity as of December 31, 2018 and 2017 are as follows (in thousands):
| Unrealized Gain (Loss) on Securities |  | Securities with Other-Than-Temporary Impairment Losses |  | Total
December 31, 2018 |  |  |  |  |
Net unrealized losses on securities available-for-sale | $ | (8,951 | ) |  | $ | — |  |  | $ | (8,951 | )
Unamortized losses on securities held-to-maturity transferred from available-for-sale | (166 | ) |  | — |  |  | (166 | )
Securities with other-than-temporary impairment losses | — |  |  | — |  |  | — |
Tax benefit | 2,644 |  |  | — |  |  | 2,644 |
Balance at December 31, 2018 | $ | (6,473 | ) |  | $ | — |  |  | $ | (6,473 | )
December 31, 2017 |  |  |  |  |
Net unrealized losses on securities available-for-sale | $ | (2,619 | ) |  | $ | — |  |  | $ | (2,619 | )
Unamortized losses on securities held-to-maturity transferred from available-for-sale | (281 | ) |  | — |  |  | (281 | )
Securities with other-than-temporary impairment losses | — |  |  | (345 | ) |  | (345 | )
Tax benefit | 841 |  |  | 100 |  |  | 941 |
Balance at December 31, 2017 | $ | (2,059 | ) |  | $ | (245 | ) |  | $ | (2,304 | )
Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income [Table Text Block] | Amounts reclassified from accumulated other comprehensive income and the affected line items in the statements of income during the years ended December 31, 2018, 2017 and 2016 , were as follows (in thousands):
| Amounts Reclassified from Other Comprehensive Income |  | Affected Line Item in the Statements of Income
| 2018 |  | 2017 |  | 2016 |
Realized gains on available-for-sale securities | $ | 901 |  |  | 616 |  |  | 1,192 |  |  | Securities gains, net (Total reclassified amount before tax)
| (261 | ) |  | (216 | ) |  | (465 | ) |  | Tax expense
Total reclassifications out of accumulated other comprehensive income | $ | 640 |  |  | $ | 400 |  |  | $ | 727 |  |  | Net reclassified amount

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- Definition Tabular disclosure of the components of accumulated other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 + Details
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